1. Field of the Disclosure
This invention relates to a method of fabricating an alignment layer of the liquid crystal display device and testing the alignment layer, and more particularly to the rapid testing method of the alignment layer and fabrication method of the alignment layer progressed in the optimum condition.
2. Description of the Related Art
A liquid crystal display device controls the transmittance of the light through a liquid crystal layer using the anisotropy of the refraction of the liquid crystal molecule to display the image. In this liquid crystal display device, the alignment layer should be rubbed to provide the alignment controlling force to the alignment layer in order to arrange the liquid crystal molecules along the desired direction.
The alignment is mainly made of an polyimide-base material. The polyimide-base polymer is reacted with a diamine compound and an anhydride in a solvent to form a polyamic acid. This polyamic acid solution is deposited on the substrate and then dehydrated through the drying and curing processes to form the polyimide thin film. In general, the polyamic acid element remains in the polyimide alignment layer when the deposited polyamic acid solution, since the polyamic acid solution is not perfectly dried. In order to dry the polyamic acid solution perfectly, the deposited polyamic acid solution should be heated for a long time, but this causes the damage of the alignment. Thus, the polyamic acid solution is heated in the predetermined period and thus the polyamic acid element remains in the polyimide alignment layer. This means that the actual alignment layer includes a polyamic acid layer and a polyimide layer.
The voltage holding ratio of the polyimide layer is high, while the voltage holding ratio of the polyamic acid layer is low. However, the polyamic acid layer has advantages of not having the direct current remain and the good boundary characteristic. Thus, if the alignment layer includes the polyamic acid layer and the polyimide layer, the alignment characteristic of the alignment layer can be improved, and the remaining of the direct current in the alignment layer can be prevented, and the adhesion between the alignment layer and the other layers contacted therewith can be improved.
The test of the alignment layer is conducted after fabricating the liquid crystal display panel. The alignment layer is tested by the MPS (Mass Product System) test which is mainly used for testing the liquid crystal display panel. This MPS test detects the line defect or the point defect of the liquid crystal display panel. In this MPS test, the gate pad and the data pad of the liquid crystal display panel are respectively connected to the gate shorting bar and the data shorting bar and the test signal is applied to the pixel through the gate shorting bar and the data shorting bar to detect the test value so that the inferiority may be judged based on the detected test value.
There are several reasons of inferiority for the liquid crystal display panel, for example, the inferiority of thin film transistor, opening of the metal pattern, and inferiority of the alignment layer. Thus, in order to understand the reason for the inferiority of a liquid crystal display panel, the user should observe the inferiority pattern of the liquid crystal display panel, take a picture of the alignment layer using a CCD camera to analyze the picture after removing the liquid crystal layer from the liquid crystal display panel, or take a picture of the thin film transistor or the metal pattern using the CCD camera to analyze the picture after removing the alignment layer from the liquid crystal display panel.
However, there are some problems with this testing method of the alignment layer.
First, there is no test process for testing solely the alignment layer in the related art. Thus, in the related art, the liquid crystal display panel should be tested as well to test the alignment layer of the liquid crystal display panel. That is, the liquid crystal display panel is completely fabricated and the test signal is inputted to the completed liquid crystal display panel to test the alignment layer. Accordingly, there is a limitation for testing the alignment layer and rapid testing is impossible.
Second, in the related art, since there is no test process for testing solely the alignment layer, various tests for the alignment layer such as testing the dry condition or the cleaning condition of the alignment layer, etc., is impossible.
Third, in the related art, since the various tests for the alignment layer is impossible, it is impossible to obtain the optimum condition for forming the alignment.